1. Field of the Invention
The present invention relates to a method of manufacturing an electron source including a large number of electron-emitting devices.
2. Related Background Art
Up to now, a surface conduction electron-emitting device has been known as an electron-emitting device. The surface conduction electron-emitting device utilizes a phenomenon that electron emission is developed by allowing a current to flow in a thin film of a small area, which is formed on a substrate, in parallel with the film surface. A structure of such a surface conduction electron-emitting device and a method of manufacturing such a device are disclosed, for example, in Japanese Patent Application Laid-Open No. 8-321254.
FIGS. 18A and 18B schematically shows the general construction of a surface conduction electron-emitting device disclosed in the above publication or the like. FIGS. 18A and 18B are a plan view and a sectional side view of the electron-emitting device, respectively. In FIGS. 18A and 18B, reference numeral 1701 denotes a substrate, 1702 and 1703 denote a pair of electrodes facing each other, 1704 denotes an electroconductive film, 1705 denotes a second gap, 1706 denotes a carbon film, and 1707 denotes a first gap.
FIGS. 17A to 17D schematically shows an example of a manufacturing process for forming an electron-emitting device having the structure shown in FIGS. 18A and 18B.
The pair of electrodes 1702 and 1703 are first formed on the substrate 1701 (FIG. 17A), followed by forming the electroconductive film 1704 for connecting between the electrodes 1702 and 1703 (FIG. 17B).
Then, an electric current is fed between the electrodes 1702 and 1703 and the so-called xe2x80x9cforming stepxe2x80x9d is performed for forming the second gap 1705 in a part of the electroconductive film 1704 (FIG. 17C).
Subsequently, in a carbon compound atmosphere, a voltage is applied between the electrodes 1702 and 1703 to perform the so-called xe2x80x9cactivation stepxe2x80x9d by which the carbon film 1706 is formed on a part of the substrate 1701 within the area of the second gap 1705 and is also formed on a part of the electroconductive film 1704 in the vicinity of the second gap 1705, resulting in an electron-emitting device (FIG. 17D). Note that, in the xe2x80x9cactivation stepxe2x80x9d, a pulse voltage is repeatedly applied between the device electrodes 1702 and 1703 in an atmosphere containing an organic substance, whereby carbon and/or carbon compound is deposited on a device.
On the other hand, Japanese Patent Laid-Open No. 9-237571 discloses another method of manufacturing a surface conduction electron-emitting device. The method comprises a step of coating an organic material film such as a thermosetting resin, or the like on an electroconductive film and a step of carbonizing the coating, instead of the above-described xe2x80x9cactivation stepxe2x80x9d.
When an electron source including a plurality of the above-described electron-emitting devices is used, an image display apparatus can be structured by combining the electron source and an image-forming member comprised of a phosphor or the like.
An electron source using conventional surface conduction electron-emitting devices roughly has the following two problems.
1) It is not necessarily easy to form a conductive film with a high accuracy in the films thickness and quality, thereby deteriorating uniformity in forming many electron-emitting devices in a flat panel display.
2) In order to form a narrow gap having good electron emission performance, many additional steps such as a step of forming an atmosphere containing an organic material, a step of precisely forming a polymer film on an electroconductive film, etc., thereby complicating control of each of the steps.
For solving the above problems, an object of the present invention is to provide a stable manufacturing method of an electron source and to provide a method of manufacturing an image-forming apparatus with no deficit and with excellent display quality at low cost.
The present invention has been made as a result of extensive studies for solving the above-mentioned problems and provides the manufacturing method described below.
That is, according to the present invention, there is provided a method of manufacturing an electron source comprising the steps of: (A) providing a substrate on which a plurality of units and wirings are arranged, each unit comprising a pair of electrodes and a polymer film for connecting the electrodes of the pair and the wirings respectively being connected to at least one of the plurality of units; (B) irradiating light onto a region of the substrate where two or more units and part of the wirings are arranged, to reduce resistivity of the polymer film in each of the two or more units; and (C) forming a gap in a film obtained by performing the step (B), wherein, at the irradiating light in step (B), a light absorptance of the wirings is lower than that of the electrodes.
The manufacturing method according to the present invention includes, as preferred aspects, xe2x80x9cthe irradiation of light is performed to all the plurality of units with sequential scanningxe2x80x9d, xe2x80x9cthe light absorptance of the wirings is lower than a light absorptance of the pair of electrodes by 15% or morexe2x80x9d, xe2x80x9ca light absorptance of the wirings is 20% or lessxe2x80x9d, and the method further includes the step of arranging a coating layer on a base layer of the wirings, for the irradiation light in the step (B), a reflectivity of the coating layer being higher than that of the base layer. In one embodiment, the gap is formed by flowing an electric current through a film obtained by the step (B).
According to the method of manufacturing an electron source of the present invention, the electrode has a relatively high light absorptance or a relatively low light reflectance at the irradiating light wavelength. Thus, light is absorbed to the electrode to cause a temperature rise efficiently, and further, the temperature of the polymer film rises due to thermal conduction to thereby promote resistance reduction. On the other hand, the wiring connected to the electrode has a relatively low light absorptance or a relatively high light reflectance. Thus, most of the light irradiated to the wiring is reflected, and the temperature rise of the wiring can be suppressed.
Note that the wavelength range, intensity, and irradiation time of the light to be irradiated are adjusted such that: the temperature rise of the wiring stops at a temperature less than a heat-resistance temperature (melting point or softening point) of the wiring; and the temperature of the electrode rises efficiently, and the temperature rise of the polymer film due to thermal conduction from the electrode to the polymer film and the light absorption of the polymer film itself transforms the polymer film to attain sufficient resistance reduction.
As a result, the image display apparatus with no deficit of a display pixel can be obtained in which the wirings are not subjected to short circuit or breaking.